Couplings are used to transmit torque and rotational movement between two machines, where the input and output shafts are misaligned axially, radially, angularly, or a combination of the aforementioned. Different types of couplings have different characteristics and are used in different applications.
Gear couplings have high torque, high misalignment, and moderate speed capability with high torsional stiffness. Gear couplings are usually lubricated by grease, which tends to remain in a cylindrical shape around the outside of the sleeve gear away from the sealing devices. Grease lubricated gear couplings with low misalignment may use contact seals outboard of the gear teeth, while high misalignment couplings may have lips on the end plates extending under the hub gear teeth. However, it is sometimes advantageous to use a lubricant that has low viscosity such as oil where it is difficult or expensive to dismantle the associated machines, to enable the lubricant to be replaced by draining and refilling the coupling using suitable plugs. However, the use of a low viscous lubricant creates sealing problems, in particular, where the couplings are subject to frequent starting and stopping applications.
One embodiment of a lubricated gear coupling is disclosed in U.S. Pat. No. 6,171,197 (Boucquey) which discloses a coupling that allows angular and radial misalignment as well as axial displacement between two shafts. The coupling comprises two hubs, a sleeve tube, stop means to prevent excessive displacement, and sealing rings. Boucquey fails to disclose or teach, however, a lubricated gear coupling with plugs that can be removed and replaced in order to drain and fill lubricant. Boucquey also fails to disclose a channel between sealing rings which aids in preventing any contaminant from entering the chamber containing the lubricant. Instead, Boucquey teaches a lubricated gear coupling with a sealing ring that experiences negligible radial displacement when misalignment occurs and is the sole means for preventing any contamination of the lubricant.
Another embodiment of a lubricated gear coupling is disclosed in U.S. Pat. No. 6,524,191 (Tennies) which discloses an inverted coupling for transmitting power between the shafts of an electric motor and a gear box pinion. The coupling has a shaft hub mounted on the motor shaft, a gearbox hub mounted on the gearbox shaft, annular splines, sleeve ring gears, and a coupling member sleeve seal. Tennies fails to disclose or teach, however, a separate contaminant excluding seal in addition to the lubricant retaining seal. Tennies also fails to disclose a channel between sealing rings which aids in preventing any contaminant from entering the chamber containing the lubricant.
Yet another embodiment of a lubricated gear coupling is disclosed in United States Application Publication No. 2011/0012314 (Nakamura) which discloses an apparatus having a first member, a second member, a first sealing body, and a second sealing body. The lubricant is sealed between the first member and the second member by the first sealing body. The second sealing body is disposed adjacent to the first sealing body opposite the lubricant and slides from a reserve position to a sealing position in the event that the first sealing body is compromised. Each sealing body includes an oil seal and a dust seal. Nakamura fails to disclose or teach, however, a lubricated gear coupling that has individual seals for retaining lubricant and excluding contaminant. Additionally, Nakamura fails to disclose plugs that can be removed and replaced in order to drain and fill the lubricant. Instead, Nakamura teaches a sealing body that has the second sealing body in a reserve position and only functions as a seal when moved into a sealing position after the first sealing body has become compromised.
Thus, there exists a long felt need for a lubricated gear coupling that contains two separate seals for retaining lubricant and excluding contaminant from the lubricant, a means for easily draining the lubricant without completely dismantling the gear coupling, and having features within the gear coupling to minimize the amount of lubricant that migrates towards the lubricant seal.